Try the Facebook marketplace as it is local and very effective. I’ve sold through it before. There’s Also an app called LetGo for selling or buying things, and I also recommend the NextDoor neighbourhood app. If you care to know about any of these do let me know. I sold my 6s Plus but I really enjoyed having it. Oh there’s also Gazelle for selling and buying used mobile phones, laptops, iPads, etc.
Hope that helps. You’ve probably found one by now!